1. Field of the Invention
The invention relates to plastisol compositions based on pulverulent organic polymers and plasticizers and adhesion-promoting additives.
2. Discussion of the Related Art
Plastisols are generally understood as meaning dispersions of organic plastics in plasticizers which gel on heating to a higher temperature and cure on cooling. The plastisols currently usual in practice quite predominantly comprise finely powdered homo- or copolymers of vinyl chloride, which are dispersed in a liquid plasticizer and form a paste. Such polyvinyl chloride plastisols (PVC plastisols) are used for the most diverse purposes. They are employed, inter alia, as sealing compositions, e.g., for seam seals on metal containers or as flange seam adhesives in the metal industry, as corrosion protection coatings for metals (for example as underseals for motor vehicles), for impregnating and coating substrates of textile materials (e.g. as a coating for carpet backing), as cable insulation, etc. Plastisols based on finely powdered methacrylate copolymers (PMMA) or styrene copolymers have also been disclosed. Such plastisols, in particular those based on PVC or PMMA, are also employed to an extensive degree in shell construction in automobile construction, for lining reinforcing structures such as engine bonnets, boot lids, doors and roof constructions, and for gluing flange seals and for sealing seams from other joining processes. Advantageous features in the use of plastisols for these intended applications are their favorable flow properties, in particular at room temperature. To ensure resistance to washers in the various cleaning, phosphating and dip-priming stages in the production of automobile chassis, these plastisol compositions are often initially gelled in a pregelling process to the extent that their viscosity is high enough to ensure this resistance to washers and an initial strength of the components.
Further additives are introduced to the plastisols, depending on the intended use. Such additives are, for example, rheology auxiliaries, stabilizers, adhesion promoters, fillers, pigments, blowing agents, reactive (capable of crosslinking) additives and water-absorbing substances. Adhesion promoters are added to the plastisols in order to effect long-term adhesion of the plastisols on steel, aluminum or galvanized and/or electrodip-coated or otherwise pretreated metal sheets. Basic compounds, such as polyaminoamides (PAA), for example, are used as adhesion promoters for PVC plastisols. Basic vinylimidazoles, which are polymerized in as comonomers, are conventionally used as adhesion promoters for polymethacrylate plastisols. Polyaminoamides are optionally added to these PMMA plastisols as an additional adhesion promoter component. Other adhesion promoter additives for plastisols are also known.
GB-A-1193896 thus describes a PVC plastisol which comprises an epoxy resin and dicyandiamide as well as α-benzyldimethyldiamine as adhesion-promoting substances. DE-A-2642514 proposes the addition of Schiff's bases and/or enamines based on polyaminoamides and epoxy resins to PVC plastisols in order to improve the adhesion thereof to metallic substrates. A large number of patent applications furthermore describes the use of polyaminoamides and derivatives and reaction products thereof as adhesion promoters for plastisols, in particular PVC plastisols, and examples which may be mentioned are DE-A-2906134, DE-A-3111815, DE-A-3201265, EP-A-171850 or EP-A-263053.
The use of blocked diisocyanate polymers, either by themselves or in combination with amine derivatives or polyaminoamide derivatives, as adhesion-promoting substances for plastisols has furthermore been proposed, and there may be mentioned by way of example EP-A-214495 or U.S. Pat. No. 5,130,402.
U.S. Pat. No. 5,039,768 proposes the use of organosilanes, acrylate monomers and unsaturated carboxylic acid monomers and epoxy resins with hardeners as adhesion-promoting additions to PVC plastisols. EP-A-343101 proposes the addition of anhydride compounds and epoxy resins to PVC plastisols, in order thereby to improve the adhesion. In a similar manner, EP-A-533026 proposes copolymers of methyl methacrylate with comonomers containing carboxyl or anhydride groups as adhesion promoters for acrylate plastisols, which can optionally comprise polyaminoamide additives. EP-A-209653 proposes reaction products of epoxy resins and low molecular weight aliphatic polyamines, in particular ethylenediamine, as adhesion-promoting additions to plastisols, in particular to plastisols based on methyl methacrylate copolymers.
In spite of a large number of proposed solutions to achieve good adhesion of plastisol compositions to the most diverse substrates, in particular metallic substrates, it is desirable to achieve, as inexpensively as possible, a permanent and ageing-resistant adhesion of plastisols which can be employed reliably as a flange seam adhesive, lining adhesive or seam seal, as a spot-welding paste or also as a coating composition, optionally with acoustic properties. The products employed in this manner should meet high corrosion protection requirements. The invention is therefore based on the object of providing inexpensive, easily available adhesion-promoting additives for plastisols which meet the current requirements of corrosion protection in automobile construction.